Clinical thermometer

ABSTRACT

A quickly responsive, dial-type clinical thermometer is provided to give fast, accurate and easily readable clinical temperatures. A temperature sensitive liquid is sealed in a sensing probe element and expands proportionately with a rise in temperature. The liquid in the probe communicates with an attached bellows which is flexed by the expanding liquid to actuate a dial indicator drivingly connected to the bellows. The indicator dial is graduated with temperature markings. A simple locking arrangement holds the indicator needle at the highest recorded temperature until reset by replacing a disposable sterile probe cover. Placement of a new cover over the probe tip automatically resets the indicator needle.

United States Patent [191 Marsilia et a1.

[451 Jan. 15, 1974 CLINICAL THERMOMETER [73] Assignee: CardinalInstruments Corporation, Cambridge, Mass.

[22] Filed: May 11, 1971 [21] App1.No.: 142,241

7/1971 Beightol 73/362 R 8/1972 Moran et a1. 73/368.4

Primary Examiner-Richard C. Queisser Assistant Examiner-Danie1 M. YasichAttorney-Morse, Altman & Oates [57] ABSTRACT A quickly responsive,dial-type clinical thermometer is provided to give fast, accurate andeasily readable clinical temperatures. A temperature sensitive liquid issealed in a sensing probe element and expands proportionately with arise in temperature. The liquid in the probe communicates with anattached bellows which is flexed by the expanding liquid to actuate adial indicator drivingly connected to the bellows. The indicator dial isgraduated with temperature markings. A simple locking arrangement holdsthe indicator needle at the highest recorded temperature until reset byreplacing a disposable sterile probe cover. Placement of a new coverover the probe tip automatically resets the indicator needle.

8 Claims, 4 Drawing Figures CLINICAL THERMOMETER BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates generally toa temperature measuring device and more particularly is directed towardsa new and improved clinical thermometer of simple, low cost constructionand compact design which does not require sterilization between use.

2. Summary of the Prior Art 'At present there are two principal types ofclinical thermometers in general use by doctors and nurses as well as inthe home. These include the conventional glass bulb mercury-filledthermometer and the more recent electronic thermometer. Theseinstruments suffer from several significant drawbacks. For example, theglass bulb thermometer has an extremely slow response time typicallyrequiring from three to five minutes to provide a reading. Furthermore,the indicated temperature is quite difficult to read because of the sizeof the instrument and the need to position the bulb at exactly the rightangle with respect to a light source before the mercury becomes visible.Furthermore, the glass bulb represents a potential hazard to patientsdue to the constant danger of breakage from the fragile glass and theinability to achieve effective sterility. The latter factor is known tobe a regular source of reinfection or cross-infection among patients.While the cost of the glass bulb thermometer is low, the vast numberused and the high rate of breakage substantially increases the cost pertemperature.

The more recent electronic thermometer employs battery power and, as aresult, its accuracy is subject to variations depending upon thecondition of the battery. Thus, to compensate for this variation, it isnecessary frequently to recalibrate the instrument. Electronicthermometers generally consist of two elements, a control indicator unitthat is carried by the operator and a cableconnected patient probe. Thiscombination is rather cumbersome in practice but more significantly, thecost of electronic thermometers generally is beyond the means of theaverage user.

Accordingly, it is an object of this invention to provide an accurateclinical thermometer which is easy to use and read, is of a simple lowcost construction requiring no maintenance and does not requiresterilization.

SUMMARY OF THE INVENTION This invention features a clinical thermometer,comprising a probe tip and a bellows communicating with one another andfilled with a temperature-responsive liquid whereby the bellows willexpand in response to heat applied to the probe tip. An indicating dialis drivingly connected to the bellows and is graduated in temperaturemarkings whereby displacement of the bellows will actuate the indicatorto visually display the monitored temperature. A locking mechanismengages the indicator mechanism for locking the indicator at therecorded temperature until released. Disposable sterile probe covers areprovided which not only protect the patient from infection but alsoresets the indicator upon replacement of the cover.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a view in perspective of aclinical thermometer made according to the invention,

FIG. 2 is a view in front elevation, partly in section, of theinstrument,

FIG. 3 is a sectional side view of a probe cover made according to theinvention, and

FIG. 4 is a detailed enlarged sectional view of the probe cover.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to thedrawings, the reference character 10 generally indicates a clinicalthermometer comprised of a housing 12 at the upper end of which is atemperature indicating dial 14 which responds to heat applied to a probetip 16 projecting from the opposite end of the housing 12. The indicator14 includes a graduated dial face 18, typically ranging from 96 to 108F,to cover the temperatures of interest normally encountered in humans,and an indicating needle 20. A disposable probe cover 22 in the .form ofa sleeve fits over the probe tip 16 to prevent patient infection andalso to actuate a reset pin 24 projecting out from the lower end of thehousing adjacent the probe tip 16. The risk of cross-infection may bereduced by fabricating the housing 12 from a self-sanitizing materialsuch as a plastic composition with a hexaclorophene additive.

Referring now more particularly to FIG. 2 there are shown details of theindicator actuating mechanism. As shown, the probe tip 16 is in the formof an elongated closed cylinder although other configurations may beemployed. The probe tip 16 is sealed to an expansible bellows 26, boththe bellows and the probe tip being filled with a temperature responsivefluid. Preferably,

the fluid employed is a liquid displaying a high coefficient of thermalexpansion such, for example, alcohol or the like. At the top of thebellows 26 is secured a hub 28 fastened to a connecting rod 30 engagingthe lower end of a stem 32 which is part of the actuating mechanism forthe dial indicator 14.,The dial indicator 14 employs conventionalgearing components well known in the art and are not shown in detail.Essentially, the linear motion of the stem 32 is converted to the rotarymotion of the indicator needle 20, the motion being a function of themonitored temperature. In order to compensate for the spring; rate ofthe'bellows 26, a spring 34 is coiled about the stem 30 and bearsagainst the shoulder portion of the hub 28 normally urging it downwardlyas viewed in FIG. 2.

The reset pin 24 extends parallel to the prove bellows and stem assemblyand engages a one-way pawl 37 which is pivoted to the inner face of theshank portion of the housing 12 and serves as a clutch in the operationof the instrument. The inner free end of the pawl 36 is urged against asmooth portion of the threaded stem 30 by means of a light spring 37 andis positioned to lock the stem at the end of its axial motion on atemperature reading. Thus, as the stem 30 moves upwardly, as viewed inFIG. 2, to its maximum temperature recording position the pawl willengage and lock the stem against retraction, thus holding the indicatorneedle at the highest recorded temperature reading. The thermometer maybe removed from the patients mouth and the temperature reading willremain visible for any length of time until the instrument is reset byan upward motion of the reset pin 24 which connects to the pawl 36 by'means of a light spring 39. The springs 37 and 39 are selected so as toallow the spring 37 to yield momentarily when the pin 24 is first pushedupwardly when a fresh cover is applied but then to quickly overcome thespring 37 to allow the pawl to reengage the stem.

It will be seen that the lower end of the reset pin 24 projects throughan opening 38 adjacent the probe tip 16 where it passes through thehousing 10. In this position, the reset pin 24 will be actuated eachtime a fresh probe cover 22 is applied over the probe tip 16. As shown,the probe cover is contoured to conform with the shape of the probe tip16 and to fit smoothly over the probe without binding. The cover 22comprises a lower sleeve portion 40 closed at its lower end and a widemouth portion 42 at its upper end adapted not only to fit over the lowerportion of the housing but also to provide a pin-engaging shoulder 44which will bear against the pin 24 when the cover 22 is fully inposition. Thus, the instrument will be reset automatically each time acover is applied and the need to reset will remind the user that afresh, sterile cover should be applied before another temperature is tobe taken. The cover 40 may be fabricated from plastic, aluminum or thelike and preferably should be of a material having good heat conductingproperties so as not to interfere with the response time of theinstrument.

Referring now more particularly to FIG. 4 of the drawings, there isshown a detail section of a probe cover made according to the invention.As shown, the walls of the probe cover are fabricated from a plasticmaterial forming a matrix 46 in which are distributed thermallyconductive metal particles 48. The inclusion of the metal particles 48in the cover wall maximizes heat conductivity so that the patientstemperature will transfer through the cover in the shortest possibletime.

While irregularly shaped metal particles may be used as a filler, betterheat transfer results may be obtained with spherical metal powders sincethere is no need to orient the particles within the matrix. Preferably,the spherical powders should have a diameter slightly less than thethickness of the wall so that the metal powder provides the major pathalong which the heat has to flow.

The metal particles may be copper or copper, tin, or silver platedpowder. Tin or silver plate is preferred to prevent oxidation of probecover which must be placed in the patients mouth.

The matrix 46 typically is a relatively stiff plastic material such asTFE and may include a self-sanitizing agent such as hexachlorophene.

By using a liquid medium which completely fills the probe and bellows,the instrument will respond to a heat source at any angle. To compensatefor nonlinearity in the expansion characteristics of the liquid and/orthe bellows, the dial 18 may be graduated in a non-linear fashion.

Having thus described the invention what I claim and desire to obtain byLetters Patent of the US. is:

l. A clinical thermometer, comprising a. a support,

b. a dial indicator mounted to said support and bearing a temperaturescale,

c. a movable indicator needle operatively connected to said indicatorproximate to said scale and movable in response to actuation of saidindicator,

d. a bellows mounted to said support,

e. a probe extending from said bellows and communicating therewith,

f. a temperature responsive fluid within said probe and bellows adaptedto expand said bellows in response to heat applied to said probe andretract on removal of heat,

g. a member slidably mounted to said support for reciprocating movementwith respect thereto and drivingly connecting said bellows to saidindicator whereby said needle will move with respect to said scale inresponse to expansion and retraction of said bellows,

h. spring means drivingly connected between said member and said supportand normally urging said member to a retracted position,

. clutch means mounted to said support and normally engageable with saidmember to prevent retraction of said member after an expansion movementof said bellows to maintain a maximum temperature indicating position ofsaid needle,

j. release means drivingly connected to said clutch means and having aportion adjacent said probe and adapted to disengage said clutch meansfrom said member when actuated to allow said member to return to astarting position, and,

k. a removable probe cover engageable with said portion for actuation ofsaid release means when in position over said probe.

2. A clinical thermometer according to claim 1 wherein said fluid is aliquid filling both said bellows and said probe.

3. A clinical thermometer according to claim 2 wherein said liquid isalcohol.

4. A clinical thennometer according to claim 1 wherein said scale isnon-linear.

5. A clinical thermometer according to claim 1 wherein said clutch meansincludes a pawl pivotally mounted to said support and. extending intoengagement with said member.

6. A clinical thermometer according to claim 5 wherein said releasemeans includes a pin engaging said pawl and adapted to pivot said pawlout of engagement with said member upon reciprocation of said pin.

7. A clinical thermometer according to claim 6 wherein said coverincludes a shoulder portion adapted to engage said pin.

8. A thermometer, comprising in combination a. a housing,

b. a temperature indicator movably mounted to said housing,

c. releasable clutch means mounted to said housing and operativelyconnected to said indicator for locking said indicator at a maximumtemperature indicating position,

d. temperature responsive drive means movably mounted to said housingand operatively connected to said indicator and adapted to move saidindicator from a start position to a temperature recording position,

e. spring means mounted to said housing engaging said drive means tourge said drive means to a start position,

f. a probe mounted to said housing and operatively connected to saiddrive means,

g. reset means movably mounted to said housing proximate to said probeand operatively connected to said clutch means and adapted on actuationto release said clutch means and allow said indicator to return to astart position.

h. a removable probe cover having a reset engaging portion adapted toengage and actuate said reset means when mounted on said probe.

t II

1. A clinical thermometer, comprising a. a support, b. a dial indicatormounted to said support and bearing a temperature scale, c. a movableindicator needle operatively connected to said indicator proximate tosaid scale and movable in response to actuation of said indicator, d. abellows mounted to said support, e. a probe extending from said bellowsand communicating therewith, f. a temperature responsive fluid withinsaid probe and bellows adapted to expand said bellows in response toheat applied to said probe and retract on removal of heat, g. a memberslidably mounted to said support for reciprocating movement with respectthereto and drivingly connecting said bellows to said indicator wherebysaid needle will move with respect to said scale in response toexpansion and retraction of said bellows, h. spring means drivinglyconnected between said member and said support and normally urging saidmember to a retracted position, i. clutch means mounted to said supportaNd normally engageable with said member to prevent retraction of saidmember after an expansion movement of said bellows to maintain a maximumtemperature indicating position of said needle, j. release meansdrivingly connected to said clutch means and having a portion adjacentsaid probe and adapted to disengage said clutch means from said memberwhen actuated to allow said member to return to a starting position,and, k. a removable probe cover engageable with said portion foractuation of said release means when in position over said probe.
 2. Aclinical thermometer according to claim 1 wherein said fluid is a liquidfilling both said bellows and said probe.
 3. A clinical thermometeraccording to claim 2 wherein said liquid is alcohol.
 4. A clinicalthermometer according to claim 1 wherein said scale is non-linear.
 5. Aclinical thermometer according to claim 1 wherein said clutch meansincludes a pawl pivotally mounted to said support and extending intoengagement with said member.
 6. A clinical thermometer according toclaim 5 wherein said release means includes a pin engaging said pawl andadapted to pivot said pawl out of engagement with said member uponreciprocation of said pin.
 7. A clinical thermometer according to claim6 wherein said cover includes a shoulder portion adapted to engage saidpin.
 8. A thermometer, comprising in combination a. a housing, b. atemperature indicator movably mounted to said housing, c. releasableclutch means mounted to said housing and operatively connected to saidindicator for locking said indicator at a maximum temperature indicatingposition, d. temperature responsive drive means movably mounted to saidhousing and operatively connected to said indicator and adapted to movesaid indicator from a start position to a temperature recordingposition, e. spring means mounted to said housing engaging said drivemeans to urge said drive means to a start position, f. a probe mountedto said housing and operatively connected to said drive means, g. resetmeans movably mounted to said housing proximate to said probe andoperatively connected to said clutch means and adapted on actuation torelease said clutch means and allow said indicator to return to a startposition, h. a removable probe cover having a reset engaging portionadapted to engage and actuate said reset means when mounted on saidprobe.